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.Dd $Mdocdate: July 13 2022 $
.Dt SSL_CTX_NEW 3
.Os
.Sh NAME
.Nm SSL_CTX_new ,
.Nm SSL_CTX_up_ref ,
.Nm TLS_method ,
.Nm TLS_server_method ,
.Nm TLS_client_method ,
.Nm SSLv23_method ,
.Nm SSLv23_server_method ,
.Nm SSLv23_client_method ,
.Nm TLSv1_method ,
.Nm TLSv1_server_method ,
.Nm TLSv1_client_method ,
.Nm TLSv1_1_method ,
.Nm TLSv1_1_server_method ,
.Nm TLSv1_1_client_method ,
.Nm TLSv1_2_method ,
.Nm TLSv1_2_server_method ,
.Nm TLSv1_2_client_method ,
.Nm DTLS_method ,
.Nm DTLS_server_method ,
.Nm DTLS_client_method ,
.Nm DTLSv1_method ,
.Nm DTLSv1_server_method ,
.Nm DTLSv1_client_method ,
.Nm DTLSv1_2_method ,
.Nm DTLSv1_2_server_method ,
.Nm DTLSv1_2_client_method
.Nd create a new SSL_CTX object as a framework for TLS enabled functions
.Sh SYNOPSIS
.In openssl/ssl.h
.Ft SSL_CTX *
.Fn SSL_CTX_new "const SSL_METHOD *method"
.Ft int
.Fn SSL_CTX_up_ref "SSL_CTX *ctx"
.Ft const SSL_METHOD *
.Fn TLS_method void
.Ft const SSL_METHOD *
.Fn TLS_server_method void
.Ft const SSL_METHOD *
.Fn TLS_client_method void
.Ft const SSL_METHOD *
.Fn SSLv23_method void
.Ft const SSL_METHOD *
.Fn SSLv23_server_method void
.Ft const SSL_METHOD *
.Fn SSLv23_client_method void
.Ft const SSL_METHOD *
.Fn TLSv1_method void
.Ft const SSL_METHOD *
.Fn TLSv1_server_method void
.Ft const SSL_METHOD *
.Fn TLSv1_client_method void
.Ft const SSL_METHOD *
.Fn TLSv1_1_method void
.Ft const SSL_METHOD *
.Fn TLSv1_1_server_method void
.Ft const SSL_METHOD *
.Fn TLSv1_1_client_method void
.Ft const SSL_METHOD *
.Fn TLSv1_2_method void
.Ft const SSL_METHOD *
.Fn TLSv1_2_server_method void
.Ft const SSL_METHOD *
.Fn TLSv1_2_client_method void
.Ft const SSL_METHOD *
.Fn DTLS_method void
.Ft const SSL_METHOD *
.Fn DTLS_server_method void
.Ft const SSL_METHOD *
.Fn DTLS_client_method void
.Ft const SSL_METHOD *
.Fn DTLSv1_method void
.Ft const SSL_METHOD *
.Fn DTLSv1_server_method void
.Ft const SSL_METHOD *
.Fn DTLSv1_client_method void
.Ft const SSL_METHOD *
.Fn DTLSv1_2_method void
.Ft const SSL_METHOD *
.Fn DTLSv1_2_server_method void
.Ft const SSL_METHOD *
.Fn DTLSv1_2_client_method void
.Sh DESCRIPTION
.Fn SSL_CTX_new
creates a new
.Vt SSL_CTX
object as a framework to establish TLS or DTLS enabled connections.
It initializes the list of ciphers, the session cache setting, the
callbacks, the keys and certificates, the options, and the security
level to its default values.
.Pp
An
.Vt SSL_CTX
object is reference counted.
Creating a new
.Vt SSL_CTX
object sets its reference count to 1.
Calling
.Fn SSL_CTX_up_ref
on it increments the reference count by 1.
Calling
.Xr SSL_CTX_free 3
on it decrements the reference count by 1.
When the reference count drops to zero,
any memory or resources allocated to the
.Vt SSL_CTX
object are freed.
.Pp
The
.Vt SSL_CTX
object uses
.Fa method
as its connection method, which can be:
.Bl -tag -width Ds
.It Fn TLS_method
The general-purpose version-flexible TLS method.
The protocol version used will be negotiated to the highest
version mutually supported by the client and the server.
The supported protocols are TLSv1, TLSv1.1, TLSv1.2, and TLSv1.3.
.It Fn DTLS_method
The version-flexible DTLS method.
The currently supported protocols are DTLSv1 and DTLSv1.2.
.El
.Pp
The following
.Fa method
arguments are deprecated:
.Bl -tag -width Ds
.It Xo
.Fn TLS_server_method ,
.Fn TLS_client_method ,
.Fn SSLv23_method ,
.Fn SSLv23_server_method ,
.Fn SSLv23_client_method
.Xc
Deprecated aliases for
.Fn TLS_method .
.It Xo
.Fn DTLS_server_method ,
.Fn DTLS_client_method
.Xc
Deprecated aliases for
.Fn DTLS_method .
.It Xo
.Fn TLSv1_method ,
.Fn TLSv1_server_method ,
.Fn TLSv1_client_method
.Xc
A connection established with these methods will only
understand the TLSv1 protocol.
.It Xo
.Fn TLSv1_1_method ,
.Fn TLSv1_1_server_method ,
.Fn TLSv1_1_client_method
.Xc
A connection established with these methods will only
understand the TLSv1.1 protocol.
.It Xo
.Fn TLSv1_2_method ,
.Fn TLSv1_2_server_method ,
.Fn TLSv1_2_client_method
.Xc
A connection established with these methods will only
understand the TLSv1.2 protocol.
.It Xo
.Fn DTLSv1_method ,
.Fn DTLSv1_server_method ,
.Fn DTLSv1_client_method
.Xc
These are the version-specific methods for DTLSv1.
.It Xo
.Fn DTLSv1_2_method ,
.Fn DTLSv1_2_server_method ,
.Fn DTLSv1_2_client_method
These are the version-specific methods for DTLSv1.2.
.Xc
.El
.Pp
In LibreSSL, the methods containing the substrings
.Dq _server
or
.Dq _client
in their names return the same objects
as the methods without these substrings.
.Pp
The list of protocols available can also be limited using the
.Dv SSL_OP_NO_TLSv1 ,
.Dv SSL_OP_NO_TLSv1_1 ,
and
.Dv SSL_OP_NO_TLSv1_2
options of the
.Xr SSL_CTX_set_options 3
or
.Xr SSL_set_options 3
functions, but this approach is not recommended.
Clients should avoid creating "holes" in the set of protocols they support.
When disabling a protocol, make sure that you also disable either
all previous or all subsequent protocol versions.
In clients, when a protocol version is disabled without disabling
all previous protocol versions, the effect is to also disable all
subsequent protocol versions.
.Pp
DTLSv1 and DTLSv1.2 can be disabled with
.Xr SSL_CTX_set_options 3
or
.Xr SSL_set_options 3
using the
.Dv SSL_OP_NO_DTLSv1
and
.Dv SSL_OP_NO_DTLSv1_2
options, respectively.
.Sh RETURN VALUES
.Fn SSL_CTX_new
returns a pointer to the newly allocated object or
.Dv NULL
on failure.
Check the error stack to find out the reason for failure.
.Pp
.Fn SSL_CTX_up_ref
returns 1 for success or 0 for failure.
.Pp
.Fn TLS_method
and the other
.Fn *_method
functions return pointers to constant static objects.
.Sh SEE ALSO
.Xr ssl 3 ,
.Xr SSL_accept 3 ,
.Xr SSL_CTX_free 3 ,
.Xr SSL_CTX_set_min_proto_version 3 ,
.Xr SSL_CTX_set_options 3 ,
.Xr SSL_CTX_set_security_level 3 ,
.Xr SSL_set_connect_state 3
.Sh HISTORY
.Fn SSL_CTX_new
first appeared in SSLeay 0.5.1.
.Fn SSLv23_method ,
.Fn SSLv23_server_method ,
and
.Fn SSLv23_client_method
first appeared in SSLeay 0.8.0.
.Fn TLSv1_method ,
.Fn TLSv1_server_method ,
and
.Fn TLSv1_client_method
first appeared in SSLeay 0.9.0.
All these functions have been available since
.Ox 2.4 .
.Pp
.Fn DTLSv1_method ,
.Fn DTLSv1_server_method ,
and
.Fn DTLSv1_client_method
first appeared in OpenSSL 0.9.8 and have been available since
.Ox 4.5 .
.Pp
.Fn TLSv1_1_method ,
.Fn TLSv1_1_server_method ,
.Fn TLSv1_1_client_method ,
.Fn TLSv1_2_method ,
.Fn TLSv1_2_server_method ,
and
.Fn TLSv1_2_client_method
first appeared in OpenSSL 1.0.1 and have been available since
.Ox 5.3 .
.Pp
.Fn DTLS_method ,
.Fn DTLS_server_method ,
and
.Fn DTLS_client_method
first appeared in OpenSSL 1.0.2 and have been available since
.Ox 6.5 .
.Pp
.Fn TLS_method ,
.Fn TLS_server_method ,
and
.Fn TLS_client_method
first appeared in OpenSSL 1.1.0 and have been available since
.Ox 5.8 .
.Pp
.Fn SSL_CTX_up_ref
first appeared in OpenSSL 1.1.0 and has been available since
.Ox 6.3 .
.Pp
.Fn DTLSv1_2_method ,
.Fn DTLSv1_2_server_method ,
and
.Fn DTLSv1_2_client_method
first appeared in OpenSSL 1.1.0 and have been available since
.Ox 6.9 .
